The background of engine governors in general, and a full disclosure of my previous invention in combined engine and load speed governors, is contained in prior U.S. patent application No. 794,615, filed May 6, 1977, now U.S. Pat. No. 4,181,103. My aforesaid engine governor was of a dynamically-surging type which allowed engine speed to oscillate rather rapidly (and forcefully for a vehicle in a lower gear ratio) about its predetermined limit.
While such oscillations are not damaging to the engine and may be helpful in encouraging a truck driver to "get out" of a lower gear ratio and into a higher ratio where the engine will be operating more efficiently, it is also advantageous to have an engine governor which allows the engine to be accelerated to its predetermined speed limit with less overshoot beyond that limit than provided by my previous dynamically-surging governor, and which will thereafter bring the engine quickly to run in close approximation to the predetermined speed limit, wandering from it only perhaps 1% when in a very low gear and less in higher gears, and that probably not on any cyclical basis. Such action is obtained basically by positioning the engine throttle to a predetermined reference position upon acceleration of the engine to a predetermined speed and actuation of the engine governor thereby, rather than by driving the throttle toward a full-closed position as in the aforesaid U.S. Pat. No. 4,181,103.
Such a smooth and gentle control is advantageous for full economy, and for driver and/or passenger comfort, especially for an application such as a school bus engine or a truck engine also used to drive a power take-off (PTO), and is typical of my present invention which provides such an engine speed governor and also combines it with a load or road speed governor essentially like that of the aforesaid U.S. Pat. No. 4,181,103. The present combination functions to safely control engine and load speeds generally like the combination of my aforesaid patent application, except smoothly without the previously-experienced dynamic-surging in engine speed control mode. However, when the smooth governing is used in a PTO governing mode, the aforementioned surging governing may be used therewith in an engine governing mode. The present invention includes an overspeed control which acts to close the throttle beyond the reference position toward a completely closed position in the event of prolonged speeding outside a normal range above the predetermined speed limit (as would be possible for a driver proceeding downhill with the accelerator pedal "floored" or calling for maximum throttle opening), thereby retaining generally the feature of my previous invention which acted to close the throttle toward a completely closed position whenever the engine speed remained anywhere above the predetermined limit.
Like my previous invention, the apparatus of the present invention is a standard unit which may be connected to the standard carburetor, ignition system, and speedometer cable of any engine and vehicle, so that it may be applied at the factory or in the field without inconvenience, and spare parts for this apparatus will be the same for any engine-vehicle combination. However, my present invention also contemplates the use of a lost-motion type overriding carburetor linkage (in place of the equally useable linkage-lengthening capsule disclosed in my aforesaid patent application) which gives a more conventional feel to the accelerator pedal, but with a more complicated parts situation, since each different engine-carburetor combination may require different linkage parts and adaptations. Also, use of a conventional pulse generator connected to the tachometer drive of a Diesel engine is contemplated for application of the apparatus of the present invention thereto.